One example of an implementation of contactless applications is based on NFC technology (Near-field Communication). These contactless applications may concern, for example, electronic transactions in banking or in public transportation, or may serve as access control and identification applications. An NFC communication is established between two non-touching entities, or two NFC entities, one operating as a contactless card and the other as a contactless card reader. In another mode, called P2P mode (Peer to Peer), two NFC entities operating as contactless cards exchange data locally and therefore play an equivalent role.
Such an NFC entity consists of a near-field communication device, referred to as an NFC device below, and an associated antenna which allows it to establish contactless communication with another NFC entity. The NFC entity operating as a contactless card may correspond to an RFID (radio frequency identification) tag, for example. Depending on the application, an NFC entity operating as a card reader may correspond, for example, to an electronic payment terminal or a machine for validating public transport tickets, or a tag reader able to identify RFID tags.
The functionalities of such a contactless entity may be supplied by a mobile telephone terminal. In this case, the mobile telephone terminal contains a subscriber identity card, or SIM card (for Subscriber Identity Module), as well as an NFC device and its associated antenna.
In this context, contactless applications, which require a certain level of security, are usually installed in the SIM card or subscriber identity card of the mobile terminal A communication can thus be established within the terminal between the contactless application of the subscriber identity card and the contactless device. Then the contactless device installed on the mobile terminal allows the mobile terminal, more specifically the application concerned, to communicate with another contactless entity in proximity to the terminal. These mobile telephones can then be used as contactless cards for example.
Certain mobile terminal architectures allow cooperation between mobile telephony functionalities and NFC functionalities (Near Field Communication).
More specifically, such a mobile terminal may comprise a microprocessor to which are connected a subscriber identity card, or SIM card, and an NFC device which is itself connected to its antenna. In this type of architecture, the NFC device is welded to a printed circuit of the mobile terminal. This architecture is therefore a rigid architecture for the NFC device and SIM card together. It is not possible to change the mobile terminal while retaining the combination of the NFC device with its antenna and the SIM card. This rigidity in the architecture therefore does not allow a subscriber of a mobile communication network to change the mobile terminal independently of the components necessary for the contactless card functionalities offered by this terminal.
A system is known in the prior art which allows more flexibility in the architecture described above. It consists of connecting the NFC device to the mobile terminal at the SIM card only. This architecture renders the mobile terminal and the NFC device physically independent and thus makes it possible to change the mobile terminal, without having to change the NFC device and SIM card, by inserting the SIM card connected to the NFC device into the new mobile terminal.
However, the voltage requirements of the NFC device and the SIM card may differ or may even be incompatible. In this case, when the NFC device is only connected to the mobile terminal at the SIM card, it can become complex to create the architecture described above. It is conventional for NFC devices to require a voltage higher than a threshold voltage of 3V for example, while SIM cards generally operate with 3V or even 1.8V.
The architecture described above requires supplying an identical voltage to the NFC device and the SIM card. Due to this, compatibility problems arise between the NFC device and the SIM card because of the different voltage requirements of SIM cards. These difficulties are further increased by the fact that most SIM cards used in NFC applications are SIM-SWP (SWP for Single Wire Protocol), which have a rated operating voltage that is generally fixed at 1.8V.